SARS: market, toilet, hospital, and laboratory.

The origin of the SARS-coronavirus (SARS-CoV) has not been pinpointed with certainty. Yet, there is circumstantial evidence that SARS is likely a zoonosis, and that the virus originated in wild mammals and crossed the species barrier to humans. The link between wild animals and humans might involve game animals that were kept and traded in wet markets in southern China. Surveillance of game animals in these markets showed that the civet cat (Paguma larvata) could be an important link. Seroprevalence of antibodies to SARSCoV is higher among traders of these game animals in Guangdong province than among control populations, including non–wild animal traders in the same markets and hospitalised patients suffering from non-respiratory diseases. Further evidence suggesting a link between SARS and game animals came from four community-acquired cases of SARS in Guangdong province in January 2004, some of which had a definite history of contact with these animals. Once the virus has infected a human, further mutations may confer it the ability to be transmitted from person-to-person with a high degree of efficiency.